Composites formed of a core of titanium, austenitic stainless steel, low carbon steel, copper, aluminum or other material having suitable ductility and which can provide desired attributes of stiffness and corrosion resistance to the composite, and outer layers of lead alloys are particularly useful for various applications including batteries, ducting, x-ray shielding, chemical plants and sound attenuation. One application of particular interest is that of battery plates for lead-acid batteries.
Electric and hybrid vehicles (i.e., vehicles having auxiliary power sources such as gasoline engines) are presently considered the most practical solution to meet increasingly tighter requirements for exhaust emission from off and on road vehicles. For these applications, at present, there are a number of power sources at various stages of development and use. These include lead/acid batteries, nickel-cadmium batteries, nickel-iron batteries, alkaline batteries and sodium-sulfur batteries. Of all the power sources being developed the lead/acid batteries are considered the most reliable and are the most widely accepted. Conventional lead/acid batteries are, at present, the most widely used electrical power source for the automotive industry (cars, vans, buses and trucks), for off-road vehicles such as fork trucks, and for recreational vehicles such as golf carts. The advantages of lead/acid batteries include low cost, high voltage per cell and good capacity life. The disadvantages of such batteries are their bulky size and heavy weight. Batteries may constitute a significant portion, as much as 20 to 30%, of the total weight of the vehicles. This limits the range and the usefulness of vehicles, both electric and hybrid, using such batteries.
A bi-polar design for lead/acid batteries is considered a solution to overcome the size and weight limitations of conventional lead/acid batteries. In this design, the battery is made up of stacks of bi-polar plates. Each plate consists of positive and negative lead active surfaces on opposite sides of a separator core material. The core material provides separation between the two surfaces of opposite polarity, rigidity to the composite plate and/or serves as a corrosion barrier to the battery acid, such as sulfuric acid. The bi-polar design incorporates grids on the lead surfaces on which active materials, such as lead oxide, are pasted. Ions discharged at the anode travel through the material and collect at the cathode at the opposite surface. The bi-polar battery thus operates in a sealed gas mode where oxygen produced at the positive side of each plate diffuses to the negative side of the adjacent plate where it is reduced.
The biggest barriers to the commercialization of the bi-polar lead/acid batteries are the technical difficulties of manufacturing the composite plates and the difficulty of producing the grids.